Exemplary embodiments of the present invention relate to a high frequency (HF) front end in a multilayer structure. This HF front end is designed for use as a transmission/reception module, transmission module or reception module.
The present invention can be used, inter alia, in active antennas (active electronically steerable antennas AESA) in radar systems, SAR (synthetic aperture radar), electronic warfare (EW) or operations command systems, as well as for navigation and communications systems. Possible platforms are ground and marine systems, aircraft, satellites, drones and missiles as well as building-based or vehicle-based systems. The multilayer structure of these modules allows for a high degree of miniaturization of the modules, as well as their arrangement in conformal and/or structurally integrated antenna arrays.
European Patent Publication No. EP 1 328 042 B1 discloses a transmission/reception module for a radar system that consists of several substrate layers stacked one above the other, which are joined by solder balls. Because of the finite extent of the solder balls, gaps remain between adjacent substrate layers. Moisture and other contaminants can penetrate into the interior of the module through these gaps, which can influence the electrical function of the individual components, e.g., electrical components, within the module or even damage them to the extent of total failure. Despite the solder connection between the individual layers described in EP 1 328 042 B1, hermetic sealing of the interior of the module is not guaranteed. This hermetic sealing is, however, required for using these modules for space travel applications and platforms in critical ambient conditions.
PCT Publication No. WO81/00949 describes a semiconducting component package comprising a chip carrier, wherein the chip carrier is constructed from a plurality of layers of insulating material. These layers comprise metallic grooves at their edges, with which electrical contact can be made with adjacent layers.
U.S. Pat. No. 5,311,402 discloses a semiconducting arrangement, wherein an integrated circuit is attached to a circuit board and a cover is provided for hermetic sealing.
U.S. Pat. No. 3,403,300 discloses a stack of circuit boards.
Protection against ambient influences is possible using external measures, such as additional welded protective casings, which increase the cross-sectional dimensions of the transmission/reception modules. In addition, mechanical forces act on the multilayer structure due to the deformation of such protective casings during welding, which influences the long-term stability of the modules or can break the solder joints between the module layers. In addition, such protective casings, e.g., of plastic (e.g., polymers), provide only limited sealing, but not hermetic sealing. Furthermore, such plastics can degas over time and thus damage the components and their joints to the substrates.
Exemplary embodiments of the present invention provide a generic HF front end (e.g., transmission/reception module with integrated radiator element) with a hermetically sealed interior space.
The HF front end according to the invention is implemented in a multilayer structure and comprises electronic components, wherein the multilayer structure contains a plurality of substrates stacked one above the other and carrying the components. The module includes grooves formed in the substrates (at the edge regions of the respective layer structure) and sealing elements (e.g. metallic frames or covers) are provided between the substrates for the purpose of hermetic sealing and are deployed within the grooves, whereby the sealing elements engage in grooves of adjacent substrates. According to the invention, adjacent substrates are soldered together.
In a first embodiment of the invention the sealing element is an open frame element, which engages in the grooves of two adjacent structures. In a second embodiment of the invention the sealing element is a closed cover element, which ensures hermetic sealing of each individual substrate (module layer).